1. The Field of the Invention
The present invention generally relates to semiconductor optical devices. In particular, the present invention relates to a semiconductor lasers having a doped active region for control of the position of the p-n junction located therein.
2. The Related Technology
Semiconductor lasers are currently used in a variety of technologies and applications, including communications networks. Examples of semiconductor lasers include Fabry-Perot (“FP”) lasers and distributed feedback (“DFB”) lasers. A DFB laser produces a stream of coherent, monochromatic light by stimulating photon emission from a solid state material. DFB lasers are commonly used in optical transmitters, which are responsible for modulating electrical signals into optical signals for transmission via an optical communication network.
Generally, a DFB laser includes a positively or negatively doped bottom layer or substrate, and a top layer that is oppositely doped with respect to the bottom layer. An active region, bounded by confinement regions, is included at the junction of the two layers. These structures together form the laser body. A coherent stream of light that is produced in the active region of the DFB laser can be emitted through either longitudinal end, or facet, of the laser body. One facet is typically coated with a high reflective material that redirects photons produced in the active region toward the other facet in order to maximize the emission of coherent light from that facet end. A grating is included in either the top or bottom layer to assist in producing a coherent photon beam. DFB lasers are typically known as single mode devices as they produce light signals at one of several distinct wavelengths, such as 1,310 nm or 1,550 nm. Such light signals are appropriate for use in transmitting information over great distances via an optical communications network.
One challenge relating to DFB and other directly modulated lasers involves accurate positioning of the p-n junction in the active layer of the device structure. Specifically, the p-n junction may not be accurately defined with respect to one or more quantum wells disposed within the active layer, which can undesirably result in a reduction in laser speed and variability in overall laser performance.
Therefore, a need exists in the art for a semiconductor optical device, such as a directly modulated DFB laser, having a well-defined p-n junction in its active layer such that it does not suffer from the above-described challenges.